An industrial Ethernet, which is also referred to as a real-time Ethernet, is a generic term for attempts to make the Ethernet standard usable for the networking of devices which are used in the industrial environment, e.g. in industrial production.
In an environment of this type, a multiplicity of devices communicating and exchanging data with one another are generally to be networked with one another. In particular, control devices, to which terminal devices or communication participants are in turn connectable, must normally be interconnected. Network devices with control functions (control device) are frequently interconnected in a ring topology for this purpose, and terminal devices or communication participants are in turn connected to a respective control device.
In the case of a ring topology, redundancy is already created from its fundamental mode of operation, according to which—expressed simply—a packet or frame or token moves along the ring and initially stops at every node of the ring. If a node wishes to transmit data, it adds a destination address of a destination node and data to the packet. The packet continues to circulate around the ring in search of the destination address. If it is found, the corresponding data are transferred out of the packet, and the circulation cycle continues as described.
In the event of a single interruption of the ring, for example due to a fault in the cabling, the packet can also pass through the ring in the opposite direction and thus still also reach all ring nodes. A double ring structure furthermore provides further protection for this purpose in that at least part of the double ring can be used as a bridge over an interrupted section of the single ring, or each of the rings of the double ring may reveal an interruption without the network being interrupted as a whole.
Substantial attention is focused in an interconnection of this type on the availability to be achieved with it. A rising degree of complexity with increasingly numerous components to be networked with one another also requires an increasingly high bandwidth and/or bit rate.
Manufacturers of control devices for spatially distributed installations or couplable vehicles, for example manufacturers of rail vehicles or systems for rail vehicles, with an increasing number of devices or control devices to be networked and/or increasingly long cable lengths, come up against limits of bus systems hitherto used, which manifest themselves, for example, in no longer adequate bandwidth for individual network participants and/or the aim to achieve a required high availability of the network.